Color photographic elements and process comprising 6-halo-7-hydroxy-1,3,4-trizaindolizines as stabilizers

ABSTRACT

A PHOTOSENSITIVE ELEMENT COMPRISING IN COMBINATION A SUPPORT CARRYING ON ONE SURFACE AT LEAST ONE SILVER HALIDE EMULSION LAYER CONTAINING A 6-HALO-7-HYDROXY-1,3,4TRIAZAINDOLIZINE AND A DYE, SAID DYE BEING A SILVER HALIDE DEVELOPING AGENT, ASSOCIATED WITH SAID EMULSION.

Jan. 19, 1971 w.'|-|. RYAN 3,556,788

COLOR PHOTOGRAPHIC ELEMENTS PROCESS COMPRISING S-HALO-V-HYDROXY-l ,5 4|- AZAINDOLIZ INES AS smsmznns I Filed Feb. 10, 1969 ;///////////,-sur=|=om HE\;\\\\\\\\\%LCYAN DYE DEVELOPER LAYER l2-///////////j\lg3 IIXE gYLVER HAYLIDE I3-\\\\\\\\\\%\INTERLAYER I v 25 l4'-//////////iVMAGENTA DYE DEVELOPER LAYER j\\ \Wfaxsmzs /\INTERILAYER vsu ow DYE DEVELOPER LAYER 5:31:55 s l ayg slLvER HALIDE OVERCOAT LAYER ZO";../ E T: E/FLUID PROCESSING CCMPOSITION 23* NEUTRALIZING LAYER ENTOR. WILL H. RYAN BY %/wum w m ATTORNEYS United States Patent 3,556,788 COLOR PHOTOGRAPHIC ELEMENTS AND PROCESS COMPRISING 6 HALO 7 HY- DROXY 1,3,4 TRIAZAINDOLIZINES AS STABILIZERS William H. Ryan, Carlisle, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Continuation-impart of application Ser. No. 513,439, Dec. 13, 1965. This application Feb. 10, 1969, Ser. No. 798,021

Int. Cl. G03c 1/34, 5/54 U.S. Cl. 96-3 11 Claims ABSTRACT OF THE DISCLOSURE A photosensitive element comprising in combination a support carrying on one surface at least one silver halide emulsion layer containing a 6-halo-7-hydroxy-1,3,4- triazaindolizine and a dye, said dye being a silver halide developing agent, associated with said emulsion.

This application is a continuation-in-part of application Ser. No. 513,439, filed Dec. 13, 1965.

The present invention relates to photography and, more particularly, to photographic products particularly adapted for employment in photographic diffusion transfer color processes.

The primary objects of the present invention are to provide photographic products, particularly adapted for employment diffusion transfer photographic color processes; to provide photographic products which include a photosensitive element which comprises a plurality of essential layers including, superposed on a common support, at least one, and preferably at least two, selectively sensitized photosensitive strata each having associated therewith, as color transfer image-forming components, a dye of predetermined color which is a silver halide developing agent; to provide photographic difiusion transfer products comprising a photosensitive element, of the last-identified type, in combination with a photographic diffusion transfer image-receiving element comprising a plurality of essential layers including a common support vide photographic diffusion transfer color processes employing photosensitive film units including, in combination, a photosensitive element and a transfer image-receptive element of the last-identified types, and a fluid photographic transfer processing composition.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, wherein the figure detailed is a diagrammatic enlarged cross-sectional view illustrating the association of elements during one stage of the performance of a diffusion transfer process, for the production of a multicolor positive transfer print, the thickness of the various materials being exaggerated.

As disclosed in US. Patent No. 2,983,606, issued May 9, 1961, a photosensitive element containing a dye developer, that is, a dye which is a silver halide developing agent, and a silver halide emulsion may be exposed and wetted by a liquid processing composition, for example,

by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element is superposed prior to, during, or after Wetting, on a sheetlike support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid processing composition, positioned intermediate the photosensitive element and the image-receiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. In unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composi tion, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element, said transfer substantially excluding oxidized dye developer. The image-receiving element receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide the reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. If the color of the transferred dye developer is affected by changes in the pH of the imagereceiving element, this pH may be adjusted in accordance with well-known techniques to provide a pH affording the desired color. The desired positive image is revealed by stripping the image-receiving layer from the photosensitive element at the end of a suitable imbibition period.

The dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

Multicolor images may be obtained using color imageforming components such as, for example, the previously mentioned dye developers, in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned US. Patent No. 2,983,606, and particularly with reference to FIG. 9 of the patents drawing, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide, emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion layer, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata are disclosed to be optionally separated from other sets by suitable interlayers, for example, by a layer of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the greensensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be employed. In such instances, a separate yellow filter may be omitted.

The dye developers are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective silver halide emulsion. Specifically, the dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution containing about 0.5 to 8%, by weight, of the respective dye developer distributed in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diffusion transfer fluid processing composition.

An extensive compilation of specific dye developers particularly adapted for employment in photographic diffusion transfer processes is set forth in aforementioned U.S. Pat. No. 2,983,606 and in the various copending U.S. applications referred to in that patent, especially in the table of U.S. applications incorporated by reference into the patent as detailed in column 27. As examples of additional U.S. patents detailing specific dye developers for photographic transfer process use, mention may also be made of U.S. Patents Nos. 2,983,605; 2,992,106; 3,047,- 386; 3,076,808; 3,076,820; 3,077,402; 3,126,280; 3,131,- 061; 3,134,762; 3,134,765; 3,135,604; 3,135,605; 3,135,- 606; 3,135,734; 3,141,772; 3,142,565; and the like.

As additional examples of synthetic, film-forming, permeable polymers particularly adapted to retain dispersed dye developer, mention may be made of nitrocarboxymethyl cellulose, as disclosed in U.S. Patent No. 2,992,-

104; an acylamidobenzene sulfo ester of a partial sulfobenzal of polyvinyl alcohol, as disclosed in U.S. Patent No. 3,043,692; polymers of N-alkyl-afi-unsaturated carboxamides and copolymers of N-alk3 l-a,5-carbxamides with N-hydroxyalkyl-a,fi-unsaturated carboxamides, as disclosed in U.S. Patent No. 3,069,263; copolymers of vinylphthalimide and a,{3-unsaturated carboxylic acids, as dis closed in U.S. Patent No. 3,061,428; copolymers of N- vinylpyrrolidones and a e-unsaturated carboxylic acids and terpolymers of N-vinylpyrrolidones, mttunsaturated carboxylic acids and alkyl esters of e rl-unsaturated carboxylic acids, as disclosed in U.S. Patent No. 3,044,873; copolymers of N,N-dialkyla,fi-unsaturated carboxamides with a,/3-unsaturated carboxylic acids, the corresponding amides of such acids, and copolymers of N-aryland N- cyc1oalkyl-a,[5'-unsaturated carboxamides with a e-unsatu- .rated carboxylic acids, as disclosed in U.S. Patent No.

3,069,264; and the like.

In addition to conventional techniques for the direct dispersion of a particulate solid material in a polymeric, or colloidal, matrix such as ball-milling and the like techniques, the preparation of the dye developer dispersion may also be obtained by dissolving the dye in an appropriate solvent, or mixture of solvents, and the resultant solution distributed in the polymeric binder, with optional subsequent removal of the solvent, or solvents, employed,

as; for example, by vaporization where the selected solvent, or solvents, possesses a sutficiently low boiling point or washing where the selected solvent, or solvents, possesses a sufficiently high differential solubility in the wash medium, for example, water, when measured against the solubility of the remaining composition components, and/ or obtained by dissolving both the polymeric binder and dye in a common solvent.

For further detailed treatment of solvent distribution systems of the types referred to above, and for an extensive compilation of the conventional solvents traditionally employed in the art to effect distribution of photographic color-providing materials in polymeric binders, specifically for the formation component layers of photographic film units, reference may be made to U.S. Patents Nos. 2,269,158; 2,322,027; 2,304,939; 2,304,940; 2,801,171; and the like.

Copending U.S. application Ser. No. 234,864, filed Nov. 1, 1962, in the name of Edwin H. Land discloses imagereceiving elements, particularly adapted for employment in the preceding diffusion transfer processes, which comprise a support layer possessing on one surface thereof, in sequence, a polymeric acid layer, preferably an inert timing or spacer layer, and an image-receiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance.

As set forth in the last-mentioned application, the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium potassium etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acidyielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. The acid-reacting group is, of course, nondiffusible from the acid polymer layer. In the preferred embodiments disclosed, the acid polymer contains free carboxyl groups and the transfer processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, being insoluble in water in the free acid form, and by forming water-soluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anyhdride groups, at least some of which preferably have been converted to free carboxyl groups prior to imbition. While the most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used. As examples of specific polymeric acids set forth in the application, mention may be made of dibasic acid half-ester derivatives of cellulose which derivatives contain free carboxyl groups, e.g., cellulose acetate hydrogen phathalate, cellulose acetate hydrogen glutarate, cellulose acetate hydrogen succinate, ethyl cellulose hydrogen succinate, ethyl cellulose acetate hydrogen succinate, cullulose acetate hydrogen succinate hydrogen phthalate; ether and ester derivatives of cellulose modified with sulfoanhyhydrides, e.g., with ortho-sulfobenzoic anhydride; polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxy or sulfo substituted aldehydres, eg., o-, m-, or pbenzaldehyde sulfonic acid or carboxylic acid; partial esters of ethylene/maleic anhydride copolymers; partial esters of methylvenyl ether/maleic anhydride copolymers; etc.

The acid polymer layer is disclosed to contain at least sufiicient acid groups to effect a reduction in the pH of the image layer from a pH of about 13 to 14 to a pH of at least 11 or lower at the end of the imbition period, and preferably to a pH of about 5 to 8 within a short time after imbition. As previously noted, the pH of the processing composition preferably is of the order of at least 13 to 14.

It is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or image transfer of unoxidized dye developers. For this reason, the pH of the image layer is kept at a level of pH 12 to 14 until the positive dye image has been formed after which the pH is reduced very rapidly to at least about pH 11, and preferably about pH 9 to 10, before the positive transfer image is separated and exposed to air. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the positive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and it is necessary that the pH of the image layer remain on the order of 12 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pH reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer. The processing technique thus effectively minimizes changes in color balance as a result of longer imbition times in multicolor transfer processes using multilayer negatives.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, by an undesired reduction in positive image density, the acid groups are disclosed to be so distributed in the acid polymer layer that the rate of their availability to the alkali is controllable, e.g., as a function of the rate of swelling of the polymer layer which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired distribution of the acid groups in the acid polymer polymer layer may be effected by mixing the acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, or by using only the acid polymer but selecting one having a relatively lower proportion of acid groups. These embodiments are illustrated, respectively, in the cited copending application, by (a) a mixture of cellulose acetate and cellulose acetate hydrogen phthalate and (b) a cellulose acetate hydrogen phthalate polymer having a much lower percentage of phthalyl groups than the first-mentioned cellulose acetate hydrogen phthalate.

It is also disclosed that the layer containing the polymeric acid may contain a Water insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats may be employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer of the aforementioned copending application, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to time control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. It was stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer, but the pH drops quite rapidly once the alkali diffuses through the spacer layer.

As examples of materials, for use as the image-receiving layer, mention may be made of solution dyeable polymers such as nylons as, for example, N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or Without plasticizers; cellulose acetate with filter as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in the copending US. application of Howard C. Haas, Ser. No. 50,848, filed Aug. 22, 1960, now US. Pat. No. 3,148,061, issued Sept. '8, 1964.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine, sodium hydroxide or sodium carbonate and the like, and preferably possessing a pH in excess of 12. Where this liquid processing composition is to be applied to the photosensitive emulsion stratum by being spread thereon, preferably in a relatively thin and uniform layer intermediate that stratum and a superposed image-receiving layer, it is disclosed to include a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, firms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular Weight polymers such as polymeric, watersoluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally, film-forming materials or thickening agents who ability to increase viscosity is substantially unaffected if left in solution for a long period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of cps. at a temperature of approximately 24 C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

For the production of the photoresponsive gelatino silver halide emulsions employed to provide the film unit, the silver halide crystals may be prepared by reacting a water-soluble silver salt, such as silver nitrate, With at least one water-soluble halide, such as ammonium, potassium or sodium bromide, preferably together with a corresponding iodide, in an aqueous solution of a peptizing agent such as a colloidal gelatin solution; digesting the dispersion at an elevated temperature, to provide increased crystal growth; washing the resultant dispersion to remove undesirable reaction products and residual water-soluble salts by chilling the dispersion, noodling the set dispersion, and washing the noodles with cold water, or, alternatively, employing any of the various systems, or procedures, adapted to effect removal of undesired components, for example, the procedures described in US. Pats. Nos. 2,614,928; 2,614,929; 2,728,662; and the like; after-ripening the dispersion at an elevated temperature in combination with the addition of gelatin and various adjuncts, for example, chemical sensitizing agents of US. Pats. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698 2,521,926; and the like; all according to the traditional procedures of the art, as described in Neblette, C. B., Photography its Materials and Processes, 6th Ed., 1962.

Optical sensitization of the emulsions silver halide crystals may be accomplished by contact of the emulsion composition with an effective concentration of the selected optical sensitizing dyes dissolved in an appropriate dispersing solvent such as methanol, ethanol, acetone, water, and the like; all according to the traditional procedures of the art, as described in Hammer, F. M., The Cyanine Dyes and Related Compounds.

Additional optional additives, such as coating aids, hardeners, viscosity-increasing agents, stabilizers, preservatives, and the like, for example, those set forth hereinafter, also may be incorporated in the emulsion formulation, according to the conventional procedures known in the photographic emulsion manufacturing art.

The photoresponsive material of the photographic emulsion will, as previously described, preferably comprise a crystal of silver, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide or silver iodobromide, of varying halide ratios and varying silver concentrations. 1

The emulsions may include the various adjuncts, or addenda, according to the techniques disclosed in the art, such as speed-increasing compounds of the quaternary ammonium type, as described in U.S. Pats. Nos. 2,271,623; 2,288,226; and 2,334,864; or of the polyethyleneglycol type, as described in U.S. Pat. No. 2,708,162; or of the preceding combination, as described in U.S. Pat. No. 2,886,437; or the thiopolymers, as described in U.S. Pats. Nos. 3,046,129 and 3,046,134.

The emulsions may also be stabilized with the salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, as described in U.S. Pats. Nos. 2,566,245 and 2,566,263; the mercury compounds of U.S. Pats. Nos. 2,728,663; 2,728,664 and 2,728,665; the triazoles of U.S. Pat. No. 2,444,608; the azindlines of U.S. Pats. Nos. 2,444,605; 2,444,606; 2,444,607; 2,450,397; 2,444,609; 2,713,541; 2,743,181; 2,716,062; 2,735,769; 2,756,147; 2,772,164 and those disclosed by Burr in Zwiss. Pot., vol. 4, 1952, pages 2-28 the disulfides of Belgian Pat. No. 569,317; the benzothiazolium compounds of U.S. Pats. Nos. 2,131,038 and 2,694,716; the zinc and cadmium salts of U.S. Pat. No. 2,839,405; and the mecapto compounds of U.S. Pat. No. 2,819,965.

Hardening agents such as inorganic agents providing polyvalent metallic atoms, specifically polyvalent aluminum or chromium ions, for example, potash alum [K Al (S 24H O] and chrome alum [Kzcl'g 4 and inorganic agents of the aldehyde type, such as formaldehyde, glyoxal, mucochloric, etc.; the ketone type such as diacetyl; the quinone type; and the specific agents described in U.S. Pats. Nos. 2,080,019; 2,725,294; 2,725,295; 2,725,305; 2,726,162; 2,732,316; 2,950,197; and 2,870,013, may be incirporated, where desired, in the selected coating solution compositions.

Coating solution compositions employed to fabricate the respective strata of the film unit may contain one or more coating aids such as saponin; a polyethyleneglycol of U.S. Pat. No. 2,831,766; a polyethyleneglycol ether of US. Pat. No. 2,719,087; a taurine of U.S. Pat. No, 2,739,- 891; a maleopimarate of U.S. Pat. No. 2,823,123; an amino acid of U.S. Pat. No. 3,038,804; a sulfosuccinamate of U.S. Pat. No. 2,992,108; or a polyether of U.S. Pat. No. 2,600,831; or a gelatin plasticizer such as glycerin; a dihydroxyalkane of U.S. Pat. No. 2,960,404; a bis-glycolic acid ester of U.S. Pat. No. 2,904,434; a succinate of U.S. Pat. No. 2,940,854; or a polymeric hydrosol of U.S. Pat. No. 2,852,386.

As the binder for the respective emulsion strata, the aforementioned gelatin may be, in whole or in part, replaced with some other colloidal material such as albumin; casein; or zein; or resins such as a cellulose derivative, as described in U.S. Pats. Nos. 2,322,085 and 2,327,808; polyacrylamides, as desrcibed in U.S. Pat. No. 2,541,474; vinyl polymers such as described in U.S. Pats. Nos. 2,253,078; 2,276,322; 2,276,323; 2,281,703; 2,310,223; 2,311,058; 2,311,059; 2,414,208; 2,461,023; 2,484,456; 2,538,257; 2,579,016; 2,614,931; 2,624,674; 2,632,704; 2,642,420; 2,678,884; 2,691,582; 2,725,296; 2,753,264, and the like.

It has now quite unexpectedly been discovered that if a silver halide emulsion having associated therewith a dye developer is specifically formulated to contain a 6-halo- 7-hydroxy-1,3,4-triazaindolizine, then significant improvement may be achieved with reference to the storage stability of a film unit retaining same and with reference to the brilliance and density of the transfer image color characteristics.

Specifically, employment of the specified triazaindolizine retaining silve halide emulsion, as a constituent component of a film unit particularly adapted for the practice of the hereinbefore described monochromatic and multichromatic transfer processes, provides significantly higher transfer image maximum dye densities and greater dye saturation over an extended storage interval.

In general, it has been found that the above-identified adjunct employed in accordance with the present invention, may be added to the emulsion at any stage during its manufacturing and/ or during the coating operation for the fabrication of a photosensitive element employing same. The addition, therefore, may be made before, during, or after the addition of the soluble silver salt to the soluble halide salt in the presence of a suitable colloid such as the preferred gelatin previously mentioned, and/or as a coating final just prior to or during the coating of the emulsion or a supporting member.

It will be recognized that the adjunct employed in accordance with the present invention may also be used in combination with additional known antifoggants and/or stabilizers such as, for example, those previously mentioned.

In general, the optimum concentration of the adjunct to be employed should be determined empirically for each specific system. However, in general, the preferred concentration falls Within the range of about 0.005 to 5.0 milligrams per gram of silver present in the silver halide emulsion, depending upon the characteristics of the silver halide emulsion formulated.

Although concentrations in excess of the first mentioned range may be employed, increasing the concentration beyond the designated limits generally provides no additional beneficial results for a conventional silver halide emulsion formulation. Conversely, concentrations below that of the designated range, however, merely decrease the effect of the adjunct below the etfective level generally sought, but do not prevent obtaining beneficial results. Where desired, however, substantial quantities of the adjunct may be employed without introducing serious desensitizing effects.

It has been specifically found that the designated adjunct, in the concentrations stated, produces the results detailed without lowering the sensitivity of the silver halide emulsion with which it is associated and/or Without reducing the sensitivity of the emulsion to light of longer wavelengths attributable to the presence of optical (spec- :tral) sensitizing dyes, when such emulsions are employed in a photographic film unit which contains, in contiguous relationship to the silver halide emulsion, a photographic color image-forming component which comprises a dye possessing a silver halide developing potential. Employment of the designated adjuncts has also disclosed no decrease in the contrast of silver halide emulsion formulations which areoptically sensitized to specified regions of the spectrum and are thus particularly adapted for use in the color diffusion transfer photographic processes detailed hereinbefore. The instant adjuncts thus clearly avoid the disadvantages prevalent when many prior art adjuncts are incorporated in the silver halide emulsion formulations which retain color image-forming components therein, or in close proximity thereto.

The adjunct of the present invention may be identified by the following functional configuration:

l OH

Preferred are those compounds possessing a chlorine or bromine group in the 6-position of the above-designated functional grouping. As examples of compounds specifically preferred for employment, mention may be made of: 5 methyl-6-bromo-7-hydroxy 1,3,4 triazaindolizine, 5- methyl-6-chloro-7-hydroxy-1,3,4-triazaindolizine, and the like.

The adjunct may be prepared in a number of ways, on of which comprises reacting approximately equimolar quantities of a 3-amino-1,2,4-triazole with a B-keto ester in a suitable solvent such as glacial acetic acid, in a manner similar to that outlined in US. Pat. No. 2,444,605, issued July 6, 1948. The solution is refluxed until condensation is complete, with the resultant 7-hydroxy-1,3,4- triazaindolizine either precipitating from solution during the course of the reaction, or being precipitated by diluting the solvent with Water, ethyl ether, acetone, or the like. If the fi-keto ester has no halo substituent on the methylene group, the product from the above reaction is halogenated by dissolving it in an inert solvent, such as water, in the presence of the selected halogen, and heating until precipitation of the desired 6-halo-7-hydroxy-1,3,4-triazaindolizine is complete. The desired adjunct may be collected by filtering the reaction mixture, and recrystallizing from a suitable solvent such as methanol or aqueous acetic acid when desired.

The fl-keto esters operable in preparing the desired adjuncts are represented by the formula:

wherein R is hydrogen or halogen; R is hydrogen, a lower alkyl, or a mononuclear aryl group; and R is a lower alkoxy group. The choice of R and R is not critical, as long as it has no deleterious effect on the herein cited improvements brought about by the adjunct.

As examples of suitable ,B-keto esters, mention may be made of acetoacetic ester, 2-chloro ethyl acetoacetate, and the like. The 3-amino-1,2,4-triazole may be substituted or unsubstituted at the 5 position, as long as the substituent is not deleterious to the herein cited improvements.

The present invention will be illustrated in greater detail in conjunction with the following examples and pro cedure which set out representative embodiments and photographic utilization of the novel monochromatic photosensitive elements of this invention, which, however, are not limited to the details therein set forth and are intended to be illustrative only.

EXAMPLE I To 84 g. (1 mole) of 3-amino-1,2,4 triazole in a 1 liter round bottom short neck flask fitted with a condenser was added 130 g. (1 mole) acetoacetic ester and 400 ml. of glacial acetic acid. The reaction mixture was heated under reflux for two hours. After precipitation was complete, the 7-hydroxy-1,3,4-triazaindolizine was collected on a Buchner funnel and washed twice with 50 ml. portions of chilled glacial acetic acid. The crude product was dried to give 110 g. (73-74% yield) of a colorless powder melting at 278-280. The crude product may be recrystallized from ethanol or water to give heavy, colorless, glistening needles which sinter at 270 and melt at 280282.

To 75 g. (0.5 mole) of 5-methyl-7-hydroxy-1,3,4-triazaindolizine in a round bottom flask was added 0.75 liter of water, and the flask heated until the triazaindolizine was completely dissolved. To this solution was added slowly, through a dropping funnel, 84 g. (0.525 mole) of bromine. After the addition of the bromine was complete, the light yellow solution was heated under reflux for an additional half hour, during which time the solution became clear. The fiocculant white 5-methyl-6-bromo-7-hydroxy-l,3,4- triazaindolizine was collected on a Buchner funnel, washed with two 50 ml. portions of warm water and dried. The

crude product, melting at 276 was recrystallized from aqueous acetic acid, with the final melting point changing very little.

EXAMPLE II To 18 g. (0.109 mole) of 2-chloro ethyl acetoacetate in 40 ml. glacial acetic acid was added 8.4 g. (0.099 mole) of 3-amino-1,2,4-triazole. The solution was stirred and refluxed for 2 hours. The resulting 5-methyl-6-chloro-7- hydroxy-l,3,4-triazaindolizine was collected on a Buchner funnel, washed with ether and acettone, dried in a desicator, and sent out for analysis.

Calculated: C, 39.05; H, 2.71; N, 30.35; Cl, 19.21. Found: C, 39.16; H, 2.80; N, 30.41; Cl, 18.98.

A plurality of photosensitive elements were prepared by coating on a gelatin subcoated cellulose triacetate film base, in succession, a layer of the cyan dye developer 1,4- bis-fi-[hydroquinonyl-u-methyl]-ethylamino) 5,8 dihydroxy-anthraquinone, dissolved in diethyl lauramide and dispersed in gelatin, at a coverage of -100 mgs./ft. of dye and mgs./ft. of gelatin, and a red-sensiitve gelatino-silver iodobromide emulsion containing a concentration of a triazaindolizine, as detailed in the following tables summarizing the results obtained, at a coverage of -300 mgs/f t. of silver and -180 mgs./ft. of gelatin.

The photosensitive elements were exposed and then processed by spreading an aqueous liquid processing composition comprising:

Water--1 00 cc.

Potassium hydroxide11.2 gm.

Hydroxyethyl cellulose (high viscosity) [commercially available from Hercules Powder Co., Wilmington, Del., under the trade name Natrasol 250]-3.8 gm.

Potassium thiosulfate-0.5 gm.

Benzotriazole3.5 gm.

N-benzyl-a-picolinium bromide-2.0 gm.

Lithium hydroxide-0.5 gm.

between each of the exposed photosensitive elements and an individual image-receiving element prepared by coating' a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine at a coverage of -600 mgs./ft. on a cellulose nitrate subcoated baryta paper to provide a polymeric image-receiving layer -0.40 mil thick. After an imbibition period of -one minute, the image-receiving element was separated and exhibited a cyan dye image.

The results obtained by employment of the test adjunct is clearly revealed and detailed by direct examination of the respective control and test transfer prints and direct comparison of same with employment of the corresponding nonhalogenated adjunct, which results are summarized below in tabular form, in the interest of clarity.

TABLE 1.5-METHYL6-BROMO-7-HYDRO XY- 1,3 .4-'1 RIAZAINDOLIZINE Fresh coatings Coatings subjected to 7 days storage at 120 F. and

70% relative humidity 1 Mgs./gn1. of silver. 2 Reflection measurement of the maximum dye density through a narrow band pass red filter.

1 Mgs./gm. of silver TAB LE 3l--5-METHYL-7-HYDR OXY-1,3,4- TRIAZAINDOLIZINE Fresh coatings Maximum sec- 2 min- Concentration l dye density ond log ute tog 1 Mgs./gm. of silver.

As will be readily observed from a comparison of the detailed tabular entries, the adjunct of the present invention unexpectedly provides significantly improved transfer image maximum dye densities over an extended period of film unit storage, even as compared with the corresponding nonhalogenated adjunct,

The instant invention is also directly concerned with a photosensitive element which comprises a common support having, positioned on one surface, at least two selectively sensitized photosensitive silver halide emulsion strata, for example, having predominant spectral sensitivity to separate regions of the visible spectrum, each having a dye of predetermined color associated therewith, for example, a predominant spectral absorption range substantially complementary to the predominant sensitivity range of the associated emulsion, and preferably separated by a spacer or interlayer.

In accordance with the teachings of the art, the positioning of the respective silver halide emulsion/ dye developer units of the configuration detailed above may be varied. However, it is generally preferred to constitute a tripack configuration in accordance with the general scheme set forth in the drawing, that is, the cyan dye developer/red-sensitive emulsion unit next contiguous the support surface and the yellow dye developer/blue-sensitive emulsion unit most distant from the support surface.

As detailed in the illustrative drawing, a selectively exposed photosensitve element 25 comprises: a support 10; a layer 11 containing a cyan dye developer; a layer 12 comprising a red-sensitive silver halide emulsion; an interlayer 13; a layer 14 containing a magneta dye developer; a layer 15 comprising a green-sensitive silver halide emulstion; an interlayer 16; a layer 17 containing a yellow dye developer; a layer 18 comprising a blue-sensitive silver halide emulsion; and a protective overcoat layer 19.

As shown in the drawing, the multilayer exposed photosensitive element 25 is shown in processing relationship with an image-receiving element 26 and a layer 20 of processing composition distributed intermediate elements and 2 6.

Image-receiving element 26 comprises: a support 24; a neutralizing layer 23; a spacer layer 22; and an imagereceiving layer 21.

As previously discussed, liquid processing composition 20 is effective to initiate development of the latent images in the respective silver halide emulsion stata. After a suitable imbition period, during which at least a portion of the dye developer associated with unexposed areas of 12 each of the emulsions is transferred to superpose imagereceiving element 26, the latter element is separated to reveal the positive multi-color image.

In a preferred embodiment of the present invention, the gelatino silver halide emulsion layers are about 0.6 to -6 microns thick, the dye-retaining layers are com posed of gelatin and are about 1 to 7 microns thick, and the polymer interlayers are 1 to 5 microns thick. With respect to a preferred image-receiving element, the imagereceiving layer is about 0.25 to 0.4 mil thick, the polymeric acid layer is about 0.3 to 1.5 mils thick, and the spacer layer is about 0.1 to 0.7 mil thick. It will be specifically recognized that the relative dimensions recited above may be appropriately modified, in accordance with the desires of the operator, with respect to the specific product to be ultimately prepared.

The present invention will be illustrated in still greater detail in conjunction with the following procedures which set out representaitve embodiments and photographic utilization of the novel multichromatic photosensitive elements of this invention, which, however, are not limited to the details therein set forth and intended to be illustrative only.

A plurality of photosensitive elements similar to that shown in the drawing may be prepared by coating, in succession, on a gelatin subbed cellulose triacetate film base, the following layers:

(1) A layer of the cyan dye developer 1,4-bis-(5-[hydroquinonyl 1x methyl] ethylamino)-5,8-dihydroxy anthraquinone dissolved in diethyl lauramide, dispersed in gelatin coated at a coverage of -159 rugs/ft. of dye and -ll9 rugs/ft. of gelatin;

(2) A red-sensitive gelatino-silver iodobromide emulsion containing 5-methyl-6-bromo-7-hydroxy-1,3,4-triazadolizine coated at a coverage of -222 rugs/ft. of silver, -04 rugs/ft. of 5-1nethyl-6-bromo-7-hydroxy-1,3,4-triazaindolizine, and -l37 mgsjft of gelatin;

(3) A layer of gelatin coated at a cover of -l'80 mgs./ft.

(4) A layer of the magenta dye developer Z-(p-[ahydroquinonylethyl]-phenylazo) 4 isopropoxy-l-naphthol, dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of -65 mgs/ft. of dye and -97 mgs./ft. of gelatin.

(5) A green-sensitive gelatino-silver iodobromide emulsion containing S-methyl-6-brorno-7-hydroxy-1,3,4-triazaindolizine coated at a coverage of -108 mgs/ft. of silver, -O.20 rngs./ft. of S-methyl-6-bromo-7-hydroxy-1,3,4-triazaindolizine, and -68 mgs./ft. of gelatin;

(6) A layer of gelatin coated at a coverage of -140 mgs./ft.

(7) A layer of the yellow dye developer 4- (p-[ot-hydroquinonylethyl1-phenylazo) 3-(N-n-hexylcarboxamido)- l-phenyl-S-pyrozolone, dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 55 mgs./ft. of dye and 69 Inga/ft. of gelatin;

(8) A blue-sensitive gelatino-silver iodobromide emulsion containing S-methyl-6-bromo-7-hydroxy-l,3,4-triazaindolizine coated at a coverage of 6 1 mgs./ft. of silver, 0.12 mg./ft. of 5-methyl-6-brorno-7-hydroxy-1,3,4-triazaindolizine, and 46 mgs./ft. of gelatin; and

(9) A layer containing 4-methylphenyl hydroquinone dissolved in diethyl lauramide, dispersed in gelatin and coated at a coverage of 10 mgs./ft. of 4'-methylphenyl hydroquinone and 30 rugs/ft. of gelatin.

Image-receiving elements were prepared according to procedure which may comprise coating a cellulose nitrate subcoated baryta paper with the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly- (ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of phosphoric acid to provide a polymeric acid layer approximately 0.75 mil thick. The external surface of the acid layer may then be coated with a 4% solution of polyvinyl alcohol in water to provide a 13 polymeric spacer layer approximately 0.3 mil thick. The external surface of the spacer layer may then be coated with a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of approximately 600 mgs./ft. to provide a polymeric image-receiving layer approximately 0.40 mil thick. The thus-prepared imagereceiving element may then be baked at 180 F. for 30 minutes and then allowed to cool.

The photosensitive elements may then be exposed and processed by spreading the aqueous liquid processing composition of the preceding example between an individual image-receiving element and each of the exposed multicolor elements, as they are brought into superposed relationship in a Polaroid Land camera. After an imbibition period of 1 minute, the picture door of the camera may be opened and the image-receiving element separated from the remainder of the film assembly.

The results which may be obtained by employment of the above-detailed procedure employing the components detailed are summarized below in tabular form, in the interest of clarity.

TABLE 4.5-METHYL-6-B ROMO-7-HYD ROX Y-1,3,4-

TABLE 5.-CONTROL Maximum dye density C eating age Cyan Magenta Yellow At room temperature:

24 hours 1.24 1. 69 1. 89

Analogous to the preceding exemplary data, it will be readily observed, from comparison of the test and control system results detailed above, that the maximum dye densities of the dyes composing the multicolor transfer prints are higher than those of the corresponding control materials.

It will be noted that the liquid processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methylaminophenol, 2,4-diaminophenol, p-benzylaminophenol, hydroquinone, toluhydroquinone, phenylhydroquinone, 4-methylphenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary or accelerating developing agents, such as a 3-pyrazolidone developing agent and a henzenoid developing agent, as disclosed in US. Patent No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of 1-phenyl-3-pyrazolidone in combination With p-benzylaminophenol and l-phenyl-3-pyrazolidone in combination with 2,S-bis-ethylenimino-hydroquinone. Such auxiliary developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in any one or more of the silver halide emulsion strata, the strata containing the dye developers, the inter-layers, the overcoat layer, the imagereceiving layer, or in any other auxiliary layer, or layers, of the film unit. It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silver halide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

In addition, development may be effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed in US. Patent No. 3,173,786.

In products employed in the diffusion transfer processes of this invention, it is preferable to expose from the emulsion side. It is, therefore, desirable to hold the photosensitive element and the image-receiving element together at one end thereof by suitable fastening means in such manner that the photosensitive element and the image-receiving element may be spread apart from their superposed processing position during exposure. A camera apparatus suitable for processing film of the type just mentioned is provided by the Polaroid Land Camera, sold by Polaroid Corporation, Cambridge, Mass, or similar camera structure such, for example, as the roll film type camera forming the subject matter of US. Patent No. 2,435,717 or the film pack type camera forming the subject matter of US. Patent No. 2,991,702. Camera apparatus of this type permits successive exposure of individual frames of the photosensitive element from the emulsion side thereof as well as individual processing of an exposed frame by bringing said exposed frame into superposed relation with a predetermined portion of the image-receiving element while drawing these portions of the film assembly between a pair of pressure rollers which require a container associated therewith and effect the spreading of the processing liquid released by rupture of said container, between and in contact with the exposed photosensitive frame and the predetermined, registered area of the image-receiving element.

It will be apparent that the relative proportions of the agents of the diffusion transfer processing composition may be altered to suit the requirements of the operator. Thus, it is within the scope of this invention to modify the herein described developing compositions by the substitution of preservatives, alkalies, silver halide solvents, etc., other than those specifically mentioned, provided that the pH of the composition is initially in excess of at least 10, for most favorable results, and most preferably in excess of 12. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of various components may be varied over a wide range and when desirable adaptable components may be disposed in the photosensitive element, prior to exposure, in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The support layers referred to may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include paper; aluminums; polymethacrylic acid, methyl and ethyl esters; vinyl chloride polymers; polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol terephthalic acid; and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate-propionate, or acetatebutyrate.

While a rupturable container provides a convenient means for spreading a liquid processing composition be tween layers of a film unit whereby to permit the processing to be carried out within a camera apparatus, the practices of this invention may be otherwise effected. For example, a photosensitive element, after exposure in suitable apparatus and while preventing further exposure thereafter to actinic light, may be removed from such apparatus and permeated with the liquid processing composition, as by coating the composition on said photosensitive element or otherwise wetting said element with the composition, following which the permeated, exposed photosensitive element, still, without additional exposure to actinic light, is brought into contact with the imagereceiving element for image formation in the manner heretofore described.

In all examples of this specification, percentages of components are given by weight unless otherwise indicated.

Throughout the specification and appended claims, the expression positive image has been used. This expression should not be interpreted in a restrictive sense since it is used primarily for purposes of illustration, in that it defines the image produced on the image-carrying layer as being reversed, in the positive-negative sense, with respect to the image in the photosensitive element. As an example of an alternative meaning for positive image, assume that the photosensitive element is exposed to actinic light through a negative transparency. In this case, the latent image in the photosensitive element will be a positive and the image produced on the image-carrying layer will be a negative. The expression positive image is intended to cover such an image produced on the imagecarrying layer.

Throughout the specification and claims, the expression superposed has been used. This expression is intended to cover the arrangement of two layers in overlying relation to each other either in face-to-face contact or in separated condition and including between them at least a layer of fluid processing composition.

It also will be recognized that, where desired, the film unit structure may also comprise an integral positive/negative construction carried on a single support.

In the preferred embodiments of the present invention, the copolymeric layer preferably has a measured thickness not less than 20% and not exceeding twice the thickness and coverage of the silver halide emulsion stratum next adjacent the support.

In addition to the described essential layers, it. will be recognized that the film unit may also contain one or more subcoats or layers, which, in turn, may contain one or more additives such as plasticizers, intermediate essential layers for the purpose, for example, of improving adhesion.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. As a product, a photosensitive element which comprises, in combination, a support layer carrying on one surface at least one silver halide emulsion layer containing a 6-halo-7-hydroxy-l,3,4-tria2aindolizine and a dye, which dye is a silver halide developing agent, associated with said emulsion.

2. As a product, a photosensitive element as defined in claim 1, wherein said 6-halo-7-hydroxy-1,3,4-triazaindolizine is methyl 6-bromo-7-hydroxy-1,3,4-triazaindolizine.

3. As :a product, a photosensitive element as defined in claim 1, wherein said 6-halo-7-hydroxy-1,3,4-triazaindolizine is 5-methyl-6-chloro-7-hydroxy-1,3,4-triazaindolizine.

4. As a product, a photosensitive element as defined in claim 1, wherein said 6-halo-7-hydroxy-l,3,4-triazaindolizine is present in a concentration within the range of about 0.005 to 5.0 milligrams of said compound per gram of silver present in said emulsion.

5. As a product, a photosensitive element as defined in claim 1, which comprises, in combination, as essential layers, a support layer carrying on one surface thereof at least two selectively sensitized gelatino silver halide emulsion layers having predominant spectral sensitivity to separate regions of the visible spectrum and each having a dye, which dye is a silver halide developing agent, associated therewith, each of which dyes has a predominant spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion, and at least one of said silver halide emulsion layers contains a compound selected from the group consisting of a 6-bromo-7-hydroxy-1,3,4-triazaindolizine and a 6- chloro-7-hydroxy-1,3,4-triazaindolizine.

6. As a product, a photosensitive element as defined in claim 1, which comprises, in combination, a plurality of essential layers including in sequence, a support layer, a cyan dye-containing layer, a red-sensitive gelatino silver halide emulsion layer, a magenta dye-containing layer, a green-sensitive gelatino silver halide emulsion layer, a yellow dye-containing layer, and a blue-sensitive gelatino silver halide emulsion layer, each of said cyan, magenta and yellow dyes being silver halide developing agents, and at least one of said emulsion layers containing a compound selected from the group consisting of 5-methyl-6- bromo7-hydroxy-1,3,4-triazaindolizine and 5-methyl-6- chloro-7-hydroxy-l,3,4-triazaindolizine.

7. A process fo forming transfer images in color which comprises the steps of exposing a photosensitive element comprising a plurality of layers including a silver halide emulsion layer containing a 6-halo-7-hydroxy-1,3,4-triazaindolizine and having associated therewith a dye, which dye is a silver halide developing agent; applying an aqueous alkaline processing composition to said exposed photosensitive element; effecting thereby development of said exposed photosensitive element; immobilizing said dye as a result of said development; forming thereby an imagewise distribution of mobile dye, as a function of the pointto-point degree of exposure of said element; and transferring, by imbibition, at least a portion of said imagewise distribution of said mobile dye to a superposed image-receiving layer to provide thereto a dye image.

8. A process of forming transfer images in color as defined in claim 7, wherein said 6-halo-7-hydroxy-1,3,4-triazaindolizine is 5-methyl-6-bromo-7-hydroxy-1,3,4-triazaindolizine.

9. A process of forming transfer images in color as defined in claim 7, wherein said 6 halo-7-hydroxy-1,3,4-triazaindolizine is 5-methyl-6-chlor-o-7-hydroxy-1,3,4-triazaindolizine.

10. A process of forming transfer images in color as defined in claim 7, which comprises the steps of exposing a photosensitive element comprising at least two selectively sensitized gelatino silver halide emulsions having predominant spectral sensitivity to separate regions of the visible spectrum and each of said emulsions having asso ciated therewith a dye, which dye is a silver halide developing agent and has a predominant spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion, and at least one of said emulsion layers containing a compound selected from the group consisting of a 6-bromo-7-hydroxy- 1,3,4-triazaindolizine and a 6-chloro-7-hydroxy-l,3,4-tri azaindolizine; applying an aqueous alkaline processing composition to said exposed photosensitive element; eifecting thereby development of each of said silver halide emulsions; immobilizing the dye associated with each of said emulsions as a result of said development; forming thereby imagewise distributions of mobile dye, as a function of the point-to-point degree of exposure of each of said emulsions; and transferring, by imbibition, at least 1 7 a portion of each of said imagewise distributions of said mobile dye to a superposed image-receiving layer to provide thereto a multicolor dye image.

11. A process of forming transfer images in color as defined is claim 7, which comprises the steps of exposing a photosensitive element which comprises blue-sensitive, green-sensitive, and redsensitive gelatino silver halide emulsion layers mounted on a common support, said bluesensitive, green-sensitive, and red-sensitive gelatino silver halide emulsions having associated therewith, respectively, yellow, magenta, and cyan dyes, each of said dyes being a silver halide developing agent and being dispersed in a separate layer next adjacent its associated emulsion intermediate said emulsion and said support, at least one of said gelatino silver halide emulsion layers containing a compound selected from the group consisting of 5-methyl- 6bromo-7-hydroxy-1,3,4-triazaindolizine and 5-methyl-6- chloro-7-hydroxy-1,3,4-triazaindolizine; applying an aqueous alkaline processing composition to said exposed photosensitive elements; eifecting thereby development of each 18 of said emulsions; immobilizing said yellow, magenta, and cyan dye, as a result of said development; forming thereby an imagewise distribution of mobile yellow, magenta, and cyan dye, as a function of the point-to-point degree of emulsion exposure; and transferring, by imbibition, at least a portion of each of said imagewise distributions of said dye to a superposed image-receiving layer to provide thereto a multicolor dye image.

References Cited UNITED STATES PATENTS 2,444,605 7/1944 Heimbach et al. 96l09 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 

